published_or_final_version / Education / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--University of Hong Kong, 1998. / Includes bibliographical references (leaves 593-645).

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

New Zealand�s lignicolous pyrenomycete flora has been little studied. The cosmopolitan Lasiosphaeriaceae, largest and least studied family in the Sordariales, has long been noted for its morphological diversity and the artificiality of its grouping. This first systematic study of lignicolous Lasiosphaeriaceae in New Zealand uses morphology and phylogenetics to elucidate relationships within the New Zealand mycota and facilitate comparisons with relatives worldwide. Collection areas spanned New Zealand�s 13 degrees of latitude and included a range of native forest types. The novel application of recently-available molecular biology techniques allowed sequencing from single pyrenomycete fruitbodies. Two new genera and 15 new species or species complexes are proposed in total. A new genus is proposed within the Lasiosphaeriaceae to accommodate an interesting new collection. Seven new species are described in the known genera Lasiosphacria and Lasiosphaeris and the polyphyly of certain Lasiosphacria taxa is discussed. Five new taxa are described within the Chaetosphaeriaceae, including a pair with surprisingly unique morphology. All are currently placed within Chaetosphaeria, but comprise part of a recently recognised long-spored clade that is sister to that which includes the type genus. Within the Helminthosphaeriaceae one new genus is proposed to accommodate an unusual new collection; and a new species described within Hilberina, but its transference to a new genus predicted as knowledge of this recent family grows. Phylogenetic results support the separation of the Chaetosphaeriaceae and Helminthosphaeriaceae from the Lasiosphaeriaceae where many of these taxa were previously. The traditional morphological character of ascospore shape is shown to have little use in the delimitation of genera. More recently emphasised characters such as peridial wall structure may have more value, however the fruitbody wall of some New Zealand taxa could not be more different from their phylogenetic relatives. New Zealand taxa are noted for their frequently unprecedented morphology and/or unique genetics in comparison with other known taxa, which are predominantly from the northern hemisphere. The high levels of morphological and genetic divergence among New Zealand taxa appear to reflect extensive microfungal endemism on these relatively isolated islands; but surveys of diversity in other parts of Gondwana are desperately needed. A Key to New Zealand taxa within the Lasiosphaeriaceae, Helminthosphaeriaceae and long-spored Chaetosphaeriaceae is provided.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

New Zealand�s lignicolous pyrenomycete flora has been little studied. The cosmopolitan Lasiosphaeriaceae, largest and least studied family in the Sordariales, has long been noted for its morphological diversity and the artificiality of its grouping. This first systematic study of lignicolous Lasiosphaeriaceae in New Zealand uses morphology and phylogenetics to elucidate relationships within the New Zealand mycota and facilitate comparisons with relatives worldwide. Collection areas spanned New Zealand�s 13 degrees of latitude and included a range of native forest types. The novel application of recently-available molecular biology techniques allowed sequencing from single pyrenomycete fruitbodies. Two new genera and 15 new species or species complexes are proposed in total. A new genus is proposed within the Lasiosphaeriaceae to accommodate an interesting new collection. Seven new species are described in the known genera Lasiosphacria and Lasiosphaeris and the polyphyly of certain Lasiosphacria taxa is discussed. Five new taxa are described within the Chaetosphaeriaceae, including a pair with surprisingly unique morphology. All are currently placed within Chaetosphaeria, but comprise part of a recently recognised long-spored clade that is sister to that which includes the type genus. Within the Helminthosphaeriaceae one new genus is proposed to accommodate an unusual new collection; and a new species described within Hilberina, but its transference to a new genus predicted as knowledge of this recent family grows. Phylogenetic results support the separation of the Chaetosphaeriaceae and Helminthosphaeriaceae from the Lasiosphaeriaceae where many of these taxa were previously. The traditional morphological character of ascospore shape is shown to have little use in the delimitation of genera. More recently emphasised characters such as peridial wall structure may have more value, however the fruitbody wall of some New Zealand taxa could not be more different from their phylogenetic relatives. New Zealand taxa are noted for their frequently unprecedented morphology and/or unique genetics in comparison with other known taxa, which are predominantly from the northern hemisphere. The high levels of morphological and genetic divergence among New Zealand taxa appear to reflect extensive microfungal endemism on these relatively isolated islands; but surveys of diversity in other parts of Gondwana are desperately needed. A Key to New Zealand taxa within the Lasiosphaeriaceae, Helminthosphaeriaceae and long-spored Chaetosphaeriaceae is provided.

"2003". / Thesis (PhD)--Macquarie University, Division of Environmental & Life Sciences, Department of Biological Sciences, 2004. / Bibliography: leaves 136-160. / Introduction: The Antarctic environment; Antarctic inhabitants; Microfungi; Identification of microfungi; Physiological factors affecting Antactic microfungi; Flow cytometry and microfungi; Hydrolytic enzymes of industrial interest; Isolation of genes from microfungi; Aims of this study -- Materials and methods: Fungal strains and cultivation conditions; Molecular identification of fungal isolates; Fungal physiology; Hydrolase activity of secreted proteins; Gene cloning and expression -- Results and discussion: Microfungal identification; Physiological factors affecting Antarctic microfungi; Activity in microfungi when grown on solid media; Characterisation of hemicellulases from selected Antarctic microfungi; Cloning of an Antarctic Penicillium allii lipase gene and its expression in Trichoderma reesei -- Conclusions and future prospects. / The Antarctic occupies that region of the planet that falls below the 60th parallel of South latitude. Although it has been frequented by adventurers, journeyman scientists and tourists for the past 100 years, the Continent has remained virtually unoccupied. The intense cold, the absence of human occupation and the limited range of local higher animal species have combined to create the impression that the Continent is virtually devoid of life. -- Although the microbiota of the Antarctic has attracted some small level of attention in the past, the examination of filamentous microfungi has been largely overlooked and fallen to a small group of dedicated investigators. In this study it will be shown that far from being an insignificant component of the Antarctic network, microfungi represent a potentially large and so far untapped bioresource. -- From just 11 bryophyte samples collected at four sites in the Ross Sea/Dry Valleys region of Southern Antarctica, some 30 microfungal isolates were recovered. Using molecular techniques, the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA (nrDNA) was sequenced to reveal no less than nine unique microfungal species. For only two of these species did the ITS sequence data produce a 100% match with records held on the public databases. This investigation also highlighted the problems inherent in the traditional morphological identification system which are now being perpetuated in the molecular database records. -- A set of seven notionally identified isolates obtained from ornithogenic soil samples gathered in the Windmill Islands in Eastern Antarctica (offshore from the Australian Antarctic Division's Casey Station) were also subjected to molecular identification based on ITS sequence data. Each of the seven isolates was identified as a unique species; six were cosmopolitan in nature and the one remaining bore very little resemblance at the molecular level to any of the recorded species although it was provided with an epithet commonly used in the identification of Antarctic microfungal species. -- To evaluate their potential as a bioresource, samples of Antarctic microfungi were examined to determine if the same physiological factors common to mesophilic species also applied to their Antarctic analogues. It is known that when placed under stress, trehalose can act as a protectant against cold (cryoprotection) and dehydration in mesophilic yeasts and fungi. The level of trehalose produced by the Antarctic isolates and their mesophilic analogues when subjected to stress was compared. A similar comparison was made for the production of glycerol which is well established as a compatible solute providing protection to mesophilic species against osmotic stress. Only in the case of trehalose production by an Antarctic Embellisia was there any indication that either of these two compounds could play a significant role in providing protection to the Antarctic fungi against the rigours of their environment, which leaves open to question what in fact does. -- In the course of investigating the means by which Antarctic microfungi guard against the damage which can ensue when subjected to oxidative stress, flow cytometry was introduced as an investigatory tool. It was established that there is a window of opportunity during which flow cytometry can be used to undertake a detailed analysis of the early stages of fungal growth from germination through hyphal development. -- Of major significance in determining the potential of Antarctic microfungi as a resource is their ability to produce new and novel enzymes and proteins. The microfungal isolates were screened for hydrolytic activity on solid media containing indicative substrates and proved to be a fruitful source of enzymes active over a range of temperatures. A detailed characterisation of two hemicellulases, β-mannanase and xylanase, secreted into a liquid medium by a subset of the Antarctic fungi and a high producing mesophilic reference strain permitted direct comparisons to be made. It was shown that the maximum hemicellulase activity of the Antarctic strains occurred at least 10°C and as much as 30°C lower than that of the reference strain and that mannanase activity for two of the Antarctic isolates exceeded 40% of their maximum at 0°C. These assay results highlight the potential of Antarctic microfungi to yield novel cold-active enzymes. -- As a final measure of the capacity of the Antarctic to yield novel enzymes from its microfungal stock, a lipase gene was selected as a target for isolation and expression in a heterologous fungal host. Using PCR techniques, the gene of interest was isolated from an Antarctic isolate of Penicillium allii, transformed into the mesophilic production host Trichoderma reesei and the active protein successfully produced in the growth medium. The recombinant lipase was assayed and found to exhibit novel characteristics consistent with a cold-adapted enzyme. / Mode of access: World Wide Web. / 186 leaves ill